backlight: pwm_bl: Fix brightness levels for non-DT case.

Enric Balletbo i Serra · Lee Jones · commit d347d0c82a99 · 2018-12-10T15:37:47.000Z
Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' allows the possibility to compute a default brightness table when there isn't the brightness-levels property in the DT. Unfortunately the changes made broke the pwm backlight for the non-DT boards. Usually, the non-DT boards don't pass the brightness levels via platform data, instead, it sets the max_brightness in their platform data and the driver calculates the level without a table. The offending patch assumed that when there is no brightness levels table we should create one, but this is clearly wrong for the non-DT case. After this patch the code handles the DT and the non-DT case taking in consideration also if max_brightness is set or not. Fixes: 88ba95b ("backlight: pwm_bl: Compute brightness of LED linearly to human eye") Reported-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
@@ -562,21 +562,50 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		goto err_alloc;
 	}
 
-	if (!data->levels) {
+	if (data->levels) {
+		/*
+		 * For the DT case, only when brightness levels is defined
+		 * data->levels is filled. For the non-DT case, data->levels
+		 * can come from platform data, however is not usual.
+		 */
+		for (i = 0; i <= data->max_brightness; i++) {
+			if (data->levels[i] > pb->scale)
+				pb->scale = data->levels[i];
+
+			pb->levels = data->levels;
+		}
+	} else if (!data->max_brightness) {
+		/*
+		 * If no brightness levels are provided and max_brightness is
+		 * not set, use the default brightness table. For the DT case,
+		 * max_brightness is set to 0 when brightness levels is not
+		 * specified. For the non-DT case, max_brightness is usually
+		 * set to some value.
+		 */
+
+		/* Get the PWM period (in nanoseconds) */
+		pwm_get_state(pb->pwm, &state);
+
 		ret = pwm_backlight_brightness_default(&pdev->dev, data,
 						       state.period);
 		if (ret < 0) {
 			dev_err(&pdev->dev,
 				"failed to setup default brightness table\n");
 			goto err_alloc;
 		}
-	}
 
-	for (i = 0; i <= data->max_brightness; i++) {
-		if (data->levels[i] > pb->scale)
-			pb->scale = data->levels[i];
+		for (i = 0; i <= data->max_brightness; i++) {
+			if (data->levels[i] > pb->scale)
+				pb->scale = data->levels[i];
 
-		pb->levels = data->levels;
+			pb->levels = data->levels;
+		}
+	} else {
+		/*
+		 * That only happens for the non-DT case, where platform data
+		 * sets the max_brightness value.
+		 */
+		pb->scale = data->max_brightness;
 	}
 
 	pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
